Arduino and related stuff (including Attiny and ESP8266) and the Raspberry Pi

Using the 4 pins of the ESP8266-01

The limited number (4) of GPIO pins on the ESP8266-01 may seem like an obstacle, for any serious application.

Yet if one uses the pins in a smart way it is very well possible to do a lot with only those 4 pins.
In some of my recent postings, I have shown the use of a DHT11 a DS18B20, an OLED, an RTC and a BMP180 with the ESP8266-01.
In this posting I set out to use 4 sensors and a display, while also uploading the acquired data to Thingspeak. It actually is expanding on a project of monitoring the atmosphere in and around my chicken coop. Yes, you could call this a weatherstation, but it is just to illustrate the use of the 4 pins, you could easily make something else this way

I will be using 2 pins for I2C (BMP180 and OLED)
1 pin for 2 DS18B20 sensors via the OneWire protocol
1 pin for the DHT11
Although the ESP8266-01 now has all its pins used, I can still add more sensors (or actuators) through the OneWire protocol and/or via the I2C protocol.

So, what do we need:BOM

ESP8266-01

2x DS18B20

1x DHT11

1x BMP180

OLED (optional)

and ofcourse a breadboard, a 3.3 V PSU and some breadboard wires and a Thingspeak acount

Just some remarks regarding the BOM:

ESP8266-01
Obviously the project is about utilizing the limited pins of the ESP8266-01, but if you still need to buy one, you could consider an ESP8266-12 that has more pins

DHT11
A cheap all purpose humidity and temperature sensor. It is not hugely accurate but it will do. If you still need to buy one, you could opt for the DHT22 that is supposedly more accurate, but you could also opt for the AM2321. That is a sort of DHT22 that is suitable for I2C, thus freeing another pin

BMP180
measures temperature and Airpressure. It is the successor of the BMP085, but it also now has some successors itself. There is the (cheaper) BMP280, but you could also opt for the BME280 that measures temperature, airpresure AND humidity. That way you can save on the DHT/AMS sensor

OLED
I just used that so I quickly could see whether the sensors were read, but you could just as well check it on Thingspeak. The OLED is too small anyway to print all the read values

The circuit

The 4 pins of the ESP8266 are not indicated as such on the PCB, and most images only clearly state GPIO0 and GPIO2.
However the ESP826-01 has a a GPIO1 pin (the Tx pin) and a GPIO3 pin (the Rx pin).
i will be using those pins as follows

GPIO0 -> SDA pin of the I2C port

GPIO1 ->DHT11

GPIO2-> SCL pin of the I2C port

GPIO3-> OneWire Bus

As my I2C modules already have pull up resistors, I will not add any I2C pullup resistors there. The DS18B20 still needs a pull up resistor for which I used a 4k7, but it is really not that critical, a 10k is also good. The DHT11 supposedly also needs a pull-up resistor but I found it to work without one as well. adding a 4k7 resistor didnt change any of the readings, so I left it out. Many of the 3 pin DHT11 modules, already have a 10 k soldered onto the module.

I just realized that I didnt draw the connections for the OLED. That is because I only hooked it up for a quick check, but should you want to add it, it is just a matter of connecting SDA to SDA and SCL to SCL… and ofcourse the ground and Vcc pins to their counterparts

The program is quite straightforward. First it sets up the libraries and the sensors.
It attaches the DHT11 to pin 1 (Tx) and the OnWire bus for the DS18B20 to pin 3 (Rx). In order to use more than 1 DS18B20 sensor on the OneWire bus, you need to know their ‘unique adress’. If you do not have that then you need a program to read those addresses. Do that on an arduino for ease.

In the program you still have to provide your WiFi credentials as well as the write API for your Thingspeak Channel

Currently this program only monitors, but what is to stop you from adding a BH1750 I2C light sensor to measure if it is evening or morning or an RTC to know the time of day and to open and close the door of the coop automatically with aid of a PCF8574 I2C I/O expansion card, or as it is already in the garden, add a PCF8591 or ADS1115 AD converter to measure soil humidity and activate a pump when necessary. Or maybe switching on the water basin heater when the temperature falls below zero
if there is an I2 C chip for it, the ESP8266 can probably use it.

NOTE: the Adafruit DHT library contains an error that may show up in bigger programs on an 8266. If the majority of readings result in “failed to read”, it is time to comment out two erroneous lines in the DHT.cpp file as in the picture below:

Note: The Rx and Tx pins sometimes can be a bit unruly when used as GPIO. If you want to use them e.g. as an output, you may want to check here.

Not offended, dont worry.
Yes line 10 needs ‘//’
but I really do not see the error in line 116. I copied the code from the page and it compiles fine. I am not sure if you put the the two dashes in front of ‘client.print’ but they are not supposed to be there.
So it really would be helpful if you tell me what error you get because I just tried and there is no error. What error do you get? What is the IDE telling you?
What would you want me to do with Pushbulet?

Hi friend, thank you very much for your post.
I was able to figure out my mistake.
Missing quotes in “GET”.
SEE PART OF THE CORRECT CODE.
// Send request to the server
client.print(String(“GET”)+url+ ” HTTP/1.1\r\n” +
“Host: ” + host + “\r\n” +
“Connection: close\r\n\r\n”);

In the past 4 years, the ESP8266 is the most popular Wifi solution for Makers, the good spec and cheap price make the competitors, such as RTL8710, hard to grow up.
But sometimes plan B is indeed needed. Recently the W600 Arm SoC Wifi solution, released by Winner Micro, we think would be an evenly matched competitor for ESP8266.